1. Field of the Invention
This invention relates to tree pruning devices and, in particular, to tree pruning devices which are operated at ground level to cut individual, overhead tree or shrub limbs.
2. Description of Related Art
Conventional tree pruning devices include a pole having a cutting member disposed at a distal end thereof. The cutting member includes a hook, having a counter cutting surface, which is positioned over the individual limb to be cut. A cutting blade is pivotably mounted with respect to the hook. The cutting blade is coupled to a rope through a series of pulleys. The rope extends the length of the pole so as to be grasped at ground level. Once the hook is placed over the limb, the rope is pulled downwardly, causing the cutting blade to pivot upwardly and cut the limb. The downward force exerted on the rope is amplified at cutting the blade by the effect of the pulleys. The larger the diameter of the tree limb(s) to be cut, the larger the manual pulling force on the rope required to sever the tree limb(s).
Thus, conventional pruning devices can require significant physical strength to operate. Further, physical endurance is also required if many tree limbs are to be pruned in a short period of time.
Devices have been developed to reduce the physical effort required to prune tree limbs. For example, U.S. Pat. No. 3,340,612 discloses an electric tree pruning saw having a motor at one end of a pole. Rotation of the motor is converted to rectilinear motion of a saw blade for sawing the limb. Although this device works well in cutting large tree limbs, it may not be effective in sawing smaller diameter limbs. Indeed, small diameter limbs must be firmly grasped while being pruned to avoid deflection of the limb. Further, rectilinear cutting blades may slip and damage limbs which are not intended or desired to be pruned.